A number of differing techniques have been developed and utilized for converting a solid cleaning composition into a concentrated cleaning solution. Examples of such cleaning solutions include detergents, rinse agents, and the like. One such employed technique uses a solid block-type cleaning composition which is placed (and thereby contained) within an enclosure. The solid block is dissolved by the impingement of a diluent upon the solid block. A common diluent is water. Use of this method typically dissolves only a portion of the solid block with each cycle. The resulting concentrated cleaning solution formed by the action of the water falls due to gravity into an underlying reservoir, or is directed by a conduit to the utilization point.
Those skilled in the art will appreciate that the utilization of solid cleaning compositions has several advantages over the use of pre-mixed liquid cleaning compositions. These advantages include that solid compositions are easier and more cost effective to ship due to its greatly-reduced weight; the solid composition requires less storage space; and the solid composition allows for a safer work environment by reducing possible splashing of hazardous chemicals. Additionally, the solid composition is more convenient for the user, and it permits easy transfer from a container to a dispenser--involving no pouring, spilling or leftover product.
A problem, however, has been encountered in the past with the foregoing dispensers. More specifically, the required and/or desired concentration of the resulting cleaning solution is maintained only as long as a minimum amount of the solid block of product is present in the dispenser prior to the activation of each cycle. When the solid block reaches a low level condition, then the resulting cleaning solution falls from the desired concentration. In one type of application, it has been empirically found that up to 200 to 300 cycles are required to reestablish the desired concentration after a low product cycle has occurred. Accordingly, there is a need to detect a low product condition level and to provide an indication of such a condition.
Despite this need, it is believed that product alarms for solid product dispensers of this type have not been utilized in the past. In other types of dispenser devices, however, measurements have been made of the resulting solution--one example being measuring the conductivity of an alkaline solution using conductivity cells. In this latter type of device, as the alkalinity decreases, the alarm sounds. Though in order to reestablish the desired concentration, the change in conductivity may occur too late in the cycle to maintain a desired constant solution concentration. Additionally, such conductivity cells are expensive and cannot be used if the solution is not conductive.
Other known types of alarms have attempted to measure colors of resulting solutions. However, color does not always produce accurate results due to wavelength variations, and so the results of such alarms have been unsatisfactory. Other devices such as thermistors, conductivity sensors, pressure sensors, vacuum, floats, and piezoelectric cells have also been attempted to be utilized in alarm devices. However, each of the foregoing has had drawbacks, and is not appropriate to the present type of dispenser since it does not directly measure the physical element which is of interest--namely the solid composition which needs periodic replenishing.
Therefore, there arises a need for a device and method in a solid to liquid dispenser for detecting a low product level, and prompting a user to replenish the solid product by providing indicia of the low product level, preferably prior to adverse impacts on the solution concentration.